Radiative forcing calculations for SF{sub 6} and CH{sub 4} using a correlated k-distribution transmission model

Abstract

A correlated k-distribution model for the atmospheric transmission of major molecular species has been used to calculate the tropospheric radiative forcing for the ground state, v{sub 3} band of SF{sub 6} and CH{sub 4}. A mid latitude summer, clear sky approximation, temperature-pressure distribution was used in the radiative transfer calculations. For the SF{sub 6} calculations a value of 0.26 W/m{sup 2} was obtained for the v{sub 3} band forcing using a new value of the measured integrated band absorption for SF{sub 6}. The abundance used was 1 ppbv of SF{sub 6}. Hot band contributions to the forcing are estimated to be on the order of three times the value of the v{sub 3} value giving a total radiative forcing of about 0.73 W/m{sup 2}. For the CH{sub 4} calculation a value of 1.71 W/m{sup 2} was obtained and this number agrees with previously published CH{sub 4} radiative forcing values to with four percent. The radiative forcing calculation for SF{sub 6} issued to estimate the global warming potential (GWP) of SF{sub 6} using an approximate model developed to provide reasonably 000 accurate GWPS. The results give GWPs for SF{sub 6} of the order of 12000--25000 (CO{sub 2} = 1). We estimate the likely range of the radiative forcing and GWP values based on two recent measurements of the total integrated band strength of SF{sub 6}. Comparison of the GWPs of SF{sub 6} to those of CF{sub 4} (3600--8500) and CFC-11 (4500--1400) indicates that SF{sub 6} has the potential to be a major greenhouse gas if large amounts are introduced into the atmosphere.